The embodiments stated herein, generally relate to the field of electric power generation from the kinetic energy of a fluid flow medium, such as wind, steam or hydraulic fluid. More specifically, the embodiments described herein relate to the development of an energy efficient wind turbine (WT) system, having a pair of contra rotors (CR) coupled to an electrical power generating alternator by means of a hydraulic power transmission (HPT) device. According to the present innovation, the integration of the contra rotor wind turbine technology with the hydraulic power transmission device (CR-WT-HPT) results in a cost effective and an energy efficient wind turbine having the following features:                reduced tower-top weight, since the low speed hydraulic pump unit need be mounted on the tower top, while the alternator could be placed on the ground level,        the rotors could start easily and safely at any wind speed, because, the heavy duty alternator inertia load is not directly connected to the rotors and moreover, the torque required to drive the hydraulic pump units can be digitally controlled to match the rotor torque at any wind speed,        increased annual energy yield per unit of rotor swept area,        Significantly reduced noise level.        
Said Contra Rotor Wind Turbine unit may comprise of conventional radially extended blades (FIG. 1a) having its axis of rotation in the direction of fluid flow, designated as CR-WT. Alternatively, each co-axial contra rotor unit may comprise of helically contoured blades having its axis of rotation, also positioned horizontally in the direction of fluid flow (FIG. 4) and designated as CR-HAWT. Still further, it may have an alternate configuration, wherein the axis of rotation of the helical bladed contra rotor may be positioned vertically up perpendicular to the flow field, designated as CR-VAWT.
As the need for energy continues to grow worldwide, the commitment to extract more of energy from the renewable sources increases. At present, the worldwide requirement is around 30 percent or more from solar and wind energy sources. For this reason, the offshore wind farm development is gaining popularity. According to the present technology, the cost of initial investment required on offshore wind turbine installations is nearly 3 to 4 times more expensive than that for the land based units. To minimize this cost, innovators are looking into several other technologies, which are more efficient and less expensive; such as:
a) The Contra Rotor Wind Turbine (CRWT, FIG. 1a), which is designed to yield nearly 30 to 50 percent more of annual energy per unit of rotor swept area, and
b) The Hydraulic Power Transmission (HPT, FIG. 1c) device that couples a rotor and an alternator. This HPT device permits the coupling of multiple rotors to a single alternator, which can be placed on the ground floor for easy access to installation and maintenance at minimal cost.
FIG. 2 shows the typical art of the present innovation, wherein the Contra Rotor (CR) technology and the hydraulic power transmission (HPT) technology are integrated to yield, a cost effective and an energy efficient wind turbine system.